Defines flow of the tabs.

<div class="definition">
    String, default = 'down'
</div>

The <span class="argument">.flow</span> can be either 'up' or 'down' and define where tabs are pointing.
<div style="height: 10px"></div>

You can defined it during object creation:
<textarea class="javascript">
let tabs = new w2tabs({
    name: 'tabs',
    flow: 'up',
    tabs: [
        { id: 'tab1', text: 'Tab 1' },
        { id: 'tab2', text: 'Tab 2' },
        { id: 'tab3', text: 'Tab 3' },
        { id: 'tab4', text: 'Tab 4' }
    ]
});
</textarea>

Or any time during run-time:
<textarea class="javascript">
w2ui.tabs.flow = 'down';
w2ui.tabs.refresh();
</textarea>